Ram air cycle machine



Dec. 15, 1959 c. R. sTElN 2,916,890

RAM AIR CYCLE MACHINE Filed July 9, 1956 2 Sheets-Sheet l raza/N5 /5 paws@ CLVE Z. 57E/N /14 BY Wa Dec. 15, 1959 vc. R. STEIN 2,916,890

RAM AIR CYCLE MACHINE Filed July 9, 1956 2 Sheets-Sheet 2 COL HOW A/OT FLOW IN VEN TOR. CZ ,V05 2. 5 75//1/ United States Patent C)n RAM AIR CYCLE MACHINE Clyde R. Stein, Los Angeles, assignments, to Crane Co., of Illinois Calif., assignor, by mesne Chicago, Ill., a corporation This invention relates to a ram air cycle machine for cooling and pressurizing the cabins" of turbine driven aircraft.

With present conventional arrangements, bleed-air from the compressor of the engine is used, and this results in cockpit contamination problems.

Also, a conventional boot-strap arrangement of compressor-heat exchanger-expansion turbine has an equilibrium rate to which the cycle settles. The machine of this invention enables control of this equilibrium rate by introducing a factor which varies the equilibrium and whichis itself controllable.

It is accordingly one object of the present invention to provide a readily controllable cooling and pressurizing machine for aircraft cabins.

It is a further object of this invention to provide a machine of the type described which is simple and economical.

It is a further object of this invention to provide such a system in which only one machine in addition to the heat exchanger is employed.

It is a feature of this invention that there is added to the conventional boot-strap cycle a turbine operating upon bleed-air from the propulsion engine of the aircraft, the rate of which is controlled by a throttle which enables running of the machine at any desired speed.

These and other objects, features and advantages will be apparent from the annexed specification in which:

Fig. 1 is a vertical section through the air cycle machine.

Fig. 2 is a schematic layout.

Fig. 3 is a simplified schematic layout.

Fig. 4 is a top view of the heat exchanger; and

Fig. 5 is a side view of the heat exchanger.

Referring now more particularly to the drawings, and particularly to Figs. 2 and 3, it will be seen that ram air from ram air inlet is caused to take two paths. Path 11 passes ram air to compressor 13, while path 12 passes ram air to an air-to-air heat exchanger 14. After being compressed in compressor 13, air passes iirst to heat exchanger 14 and thence to expansion turbine 15, from whence it passes into cabin 16. The compressor rotor, turbine rotor and the rotor of a power turbine are all mounted on a single shaft 20.

Air from the propulsion engine .is passed rst to a variable throttle or valve 21 and is then passed to the power turbine 17, after which it is vented overboard.

Referring now to Figs. 1, 4 and 5, it will be seen that two pieces of apparatus, other than controls and conduits, are all that are required, i.e. the machine of Fig. l and the heat exchanger of Figs. 4 and 5. The heat exchanger 14 is largely conventional and consists of a shell in which air from branch 10 is passed in one direction through the exchanger and then is ventedroverboard, while hot air from compressor 13 is passed countercurrent and thence to the cooling turbine 15.

Referring now to Fig. 1, the machine there shown 2,916,890 Paten'tetipDec. 15, 1959 includes the compressor 13, power turbine 17 and cooling turbine .15 all mounted on a common shaft 20. The compressor 13 includes vanes 40. The shaft 20 is surrounded by an oil reservoir 41 in which is positioned a lubricating wick 42, and the shaft is journaled in bearings 43 and 44, the bearing 44 being retained by a coil spring 45 abutting a shoulder 46 inthe tube 47 forming part of the housing. The bearing 43 abuts a shoulder 48 as indicated. Oil slingers 49 and 50 return oil through the passages 51l and 52 to the oil reservoir. The power turbine 17 has an intake manifold 53 and an exhaust manifold 54. The cooling turbine 13 includes a turbine wheel 55, blades 56 and variable nozzles 57.

In order to properly controllthis system, four control elements are employed: a temperature sensor 30 which is arranged to vary the position of nozzle 31 of the cooling turbine; a variable throttle 21 upstream from power turbine 17 controlled by mass iiow sensor 34; a minimum incidence vane positioner 32 for controlling the position of the vanes of compressor 13; and finally a speed limiter 33 arranged to overriderthrottle 21 when cooling requirements call for a speed in excess of the design limitations of the unit. The minimum incidence vane positioner 32 is a conventional device for positioning the vanes 40 So as to equalize pressures on both sides thereof, i.e. the vanes are aligned with the flow and may take the form of any of the well-known devices for so aligning the vanes.

Operation of the above described unit is as follows. Should the cabin have a lower temperature than is desired, temperature sensor 30 signals the vanes of cooling turbine 15 to a larger angle, decreasing the back pressure on the compressor, lowering the expansion head available to the cooling turbine and thus increasing the inlet temperature in the cabin. A raise in mass ow causes mass flow sensor 34 to signal throttle 21 towards a more closed position, which reduces over-al1 power and permits the machine to seek equilibrium at a lower operating speed.

When increased cooling capacities are required, the cabin temperature sensor 30 signals the cooling turbine nozzle actuator 31, decreasing nozzle angles and therefore the effective nozzle area. With a smaller cooling turbine nozzle area, the back pressure on the compressor 13 is raised, the mass iiow decreasing accordingly. The mass ow sensor 34, sensing a decrease in mass iiow, signals the power turbine throttle 21 causing it to open, providing an increase in power, and accelerating the air cycle machine until scheduled flow rate is again maintained. The additional head provided by the compressor when expanded across the cooling turbine 15 provides for lower discharge temperatures.

At high altitudes, especially when maximum cooling loads exist, the machine will be called upon to operate at maximum r.p.m. Since stress limitations dictate maximum tip speed of the compressor, it is necessary to incorporate a speed limiting control which will restrict the power turbine to operational speeds within these limits. To this end there is incorporated in the device a speed limiter 33 which may be in any of the conventional forms of governor capable of generating a signal, which signal is imparted as indicated by the broken line in Figure 2 to the throttle 21. The signal thus imposed is inactive until its value reaches a certain minimum which can be determined in various conventional ways such as by causing the signal to be of suicient strength to overcome a presetspring or the like. Thus the mass iow sensor 34 is in control of the throttle 21 until the speed limiter signal takes over, and thereafter it is the signal from the speed limiter which governs until this signal becomes too weak to reach the preset minimum. In addition, since the compressor must handle a range of volume flows, unobtainable with a fixed vane design, it is necessary to incorporate a variable diffuser vane control which internally adjusts these vanes for minimum incidence with the impinging ow. In this manner the required compressor characteristic can be obtained.

While there has been described what is at present considered the preferred embodiment of the invention, t'will be understood that various changes and alterations may be made therein without departing from the essence of the invention and it is intended to cover herein all such changes and alterations as come within the true scope and spirit of the annexed claims.

I claim:

1. A cooling and pressurizing system for the cabin of an aircraft of the type having a propulsion engine forming a source of bleed compressed air and another source of ram air comprising: a single shaft; a rotary compressor, a power turbine and an expansion turbine all mounted on said shaft; an airto-air heat exchanger; conduit means for conducting ram air successively to said compressor, to said heat exchanger, to said expansion turbine and to said cabin; conduit means for conducting bleed air to Said power turbine and thence to atmosphere; a variable throttle in said last mentioned conduit means upstream from said power turbine to control the ow of said bleed air; a flow sensor in said first conduit means arranged to control said variable throttle; and conduit means conducting a portion of said ram air to said heat exchanger in cooling relation to ar from said compressor.

2. A cooling and pressurizing system for the cabin of an aircraft of the type having a propulsion engine forming a source of bleed compressed air and another source of ram air comprising: a single shaft; a rotary compressor, a power turbine and an expansion turbine all mounted on said shaft; an air-to-air heat exchanger; conduit means for conducting ram air successively to said compressor, to said heat exchanger, to said expansion turbine and to said cabin; conduit means for conducting bleed air to said power turbine and thence to atmosphere; a variable throttle in said last mentioned conduit means upstream from said power turbine to control the flow of said bleed air; a mass flow sensor in said first conduit means between said expansion turbine and said cabin arranged to control said variable throttle; and conduit means conducting a portion of said ram air to said heat exchanger in cooling relation to air from said compressor.

3. A system as Set forth in claim 2 in which Said expansion turbine is of the variable nozzle position type and said cabin is provided with a temperature sensor arranged to variably adjust said nozzle position in accordance with temperature conditions in said cabin.

References Cited in the file of this patent UNITED STATES PATENTS 2,509,899 Wood May 30, 1950 2,557,099 Green June 19, 1951 2,767,561 Seeger Oct. 23, 1956 

